 start = element library { library-content }
 
 library-content = element book { book-content }+
 
 book-content = 
    attribute id { text },
    attribute available { text },
    element isbn { isbn-content },
    element title { title-content },
    element author { author-content }*,
    element character { character-content }*
 
 author-content = 
    attribute id { text },
    element name { name-content },
    element born { born-content },
    element dead { dead-content }?
 
 born-content = text
 
 character-content = 
    attribute id { text },
    element name { name-content },
    element born { born-content },
    element qualification { qualification-content }
 
 dead-content = text
 
 isbn-content = text
 
 name-content = text
 
 qualification-content = text
 
 title-content = attribute xml:lang { text }, text
